1. Field of the Invention
The present invention generally relates to semiconductor devices, and more particularly to a method and apparatus for forming a semiconductor device using MOCVD (metalorganic chemical vapor deposition).
2. Description of the Related Art
CVD or MOCVD apparatuses are widely used in the process of manufacturing semiconductor devices as film-forming apparatuses. For instance, the CVD apparatuses are used to form a variety of oxide and polysilicon films, while the MOCVD apparatuses are used to form a compound semiconductor film by epitaxial growth.
Recently, a semiconductor device using a ferroelectric or high-K dielectric film, such as a ferroelectric memory device, has started to be used.
Conventionally, a ferroelectric or high-K dielectric film employed in a semiconductor device such as a ferroelectric memory device is temporarily formed in an amorphous phase and then is crystallized by heat treatment. According to such a method, however, film deposition and crystallization should be performed separately. Further, a variety of problems occur due to heat treatment at high temperatures in an oxygen atmosphere employed for the process of crystallizing the amorphous phase.
In recent years, therefore, a technology of depositing a ferroelectric or high-K dielectric film directly in the form of a crystallized film by CVD has been studied. Particularly, in the case of forming a ferroelectric or high-K dielectric film, a variety of organometallic compounds including the component metal elements of the ferroelectric or high-K dielectric film should be used as material. That is, in the case of forming a ferroelectric or high-K dielectric film by CVD, MOCVD is employed.
FIG. 1 is a diagram showing the configuration of a conventional CVD film-forming apparatus 11 used for forming a ferroelectric or high-K dielectric film by CVD.
According to FIG. 1, the CVD film-forming apparatus 11 includes a CVD film-forming chamber 12 and first and second material gas supply lines 14A and 14B. The CVD film-forming chamber 12, which is evacuated by an exhaust system 13, includes a stage 12A holding a substrate to be processed (hereinafter a processing substrate). The first material gas line 14A supplies the CVD film-forming chamber 12 with oxygen gas as part of material gas. The second material gas line 14B supplies the CVD film-forming chamber 12 with organometallic compounds as material gas. The material gas line 14B includes a valve V1 that is opened and closed to control the supply of the organometallic compounds in the material gas line 14B to the CVD film-forming chamber 12 and a valve V2 bypassing the organometallic compounds to the exhaust system 13. Further, a substrate conveying chamber 15 which the processing substrate is conveyed to or from is connected to the CVD film-forming chamber 12.
In the CVD film-forming apparatus 11, after the processing substrate is introduced into the substrate conveying chamber 15, the organometallic compounds in the material gas line 14B are bypassed through the valve V2 to the exhaust system 13 while the processing substrate is heated up to a desired processing temperature. The formation of an initial layer immediately after the start of film formation can be prevented by providing the bypass valve V2.